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331.
A theoretical study on the stability difference of the borane
and carborane C2Bn−2Hn (5 ≤ n ≤ 7) clusters
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In order to study the electronic structure and structural stability of borane and carborane C2Bn?2Hn (5 ≤ n ≤ 7) clusters, especially the stability difference between the borane and carborane C2B3H5. The frontier orbital energy levels of the borane and carborane C2Bn?2Hn (5 ≤ n ≤ 7) clusters are calculated at CCSD(T)/aug‐cc‐pVXZ//B3LYP/def2‐TZVPP level. The results are further analyzed by qualitative frontier orbital method based on the cap–ring interaction. The results reveal that: (1) the larger Egap(HOMO‐LUMO energy gap) of carborane C2Bn?2Hn (5 ≤ n ≤ 7) clusters than borane (5 ≤ n ≤ 7) clusters originates from the more effective cap–ring orbital overlap of carborane C2Bn?2Hn (5 ≤ n ≤ 7) clusters than that of borane (5 ≤ n ≤ 7) clusters; (2) the smallest Egap of the borane results from the highest energy level of the ring symmetry‐adapted linear combination orbital of cluster; and (3) the largest Egap of the carborane C2B3H5 is induced by the most effective cap–ring orbital interaction of C2B3H5 cluster. © 2014 Wiley Periodicals, Inc. 相似文献
332.
采用简单的原位还原合成方法,利用具有温和还原性能的氨硼烷作为还原剂,在室温下一步还原氧化石墨烯和氯化钴混合溶液制备了还原氧化石墨烯负载钴纳米复合材料催化剂. 利用所制备的钴/还原氧化石墨烯催化剂催化氨硼烷水解制氢,发现钴/还原氧化石墨烯具有优异的催化性能. 相对于没有负载的钴纳米粒子以及采用硼氢化钠作为还原剂制备的钴/还原氧化石墨烯催化剂,采用氨硼烷还原制备的钴/还原氧化石墨烯催化剂表现出更加优越的催化性能. 动力学测试表明,钴/还原氧化石墨烯催化氨硼烷水解反应为零级反应,同时钴/还原氧化石墨烯催化剂催化氨硼烷水解反应的活化能为27.10 kJ·mol-1,低于大部分已报道的其它催化剂,甚至一些贵金属催化剂的活化能. 钴/还原氧化石墨烯催化剂有着稳定的循环使用性,特别是其具有的磁性使得它能够直接从溶液中通过磁力回收,极具应用前景. 这种简单有效的合成方法有望推广到其它的金属-还原氧化石墨烯纳米复合材料体系. 相似文献
333.
The coupling of aldehydes or ketones with (2-(4-methoxyphenyl)-4-methylenetetrahydrofuran-3-yl)methanol in the presence of nitriles under the influence of 5 mol % tris(pentaflourophenyl)borane at room temperature afforded a novel series of cis-fused hexahydro-1H-furo[3,4-c]pyran derivatives in good yields with high selectivity. This is the first report on the synthesis of hexahydro-1H-furo[3,4-c]pyranyl amide through a sequential Prins/Ritter reactions using B(C6F5)3 as a mild Lewis acid. 相似文献
334.
A simple and efficient protocol is developed for the synthesis of 5-substituted 1H-tetrazole derivatives from various nitriles and sodium azide (NaN3) via [3+2] cycloaddition reaction using B(C6F5)3 as a catalyst. The present synthetic method displayed significant advantages such as low catalyst loading, mild reaction conditions, low toxicity, easy work-up, high yields, and compatibility with other functional groups. 相似文献
335.
Audrey Ledoux Dr. Paolo Larini Dr. Christophe Boisson Dr. Vincent Monteil Dr. Jean Raynaud Dr. Emmanuel Lacôte 《Angewandte Chemie (International ed. in English)》2015,54(52):15744-15749
The one‐step polycondensation of diamines and diboranes triggered by the in situ deprotonation of the diammonium salts and concomitant reduction of bisboronic acids leads to the assembly of polymer chains through multiple Lewis pairing in their backbone. These new polyboramines are dihydrogen reservoirs that can be used for the hydrogenation of imines and carbonyl compounds. They also display a unique dihydrogen thermal release profile that is a direct consequence of the insertion of the amine–borane linkages in the polymeric backbone. 相似文献
336.
Miosz Frydrych Daria Pakua Bogna Sztorch Dariusz Brzkalski Robert E. Przekop Bogdan Marciniec 《Molecules (Basel, Switzerland)》2021,26(14)
The functionalization of mono- and octahydrospherosilicate with vinylboranes and allylboranes via hydrosilylation reaction in the presence of a Karstedt’s platinum (0) catalyst is presented. This is the catalytic route to obtain a new class of silsesquioxanes containing boron atoms in their structure in high yields (>90%) and with satisfactory selectivity. The obtained compounds were fully characterized by spectroscopic (1H, 13C, 29Si NMR) and spectrometric methods (MALDI-TOF-MS), as well as thermal analysis (TGA). The obtained compounds were subjected to thermal tests, characterizing the processes of melting, thermal evaporation, sublimation and thermal decomposition. 相似文献
337.
Célia BillaudJean-Philippe Goddard Thierry Le Gall Charles Mioskowski 《Tetrahedron letters》2003,44(24):4451-4454
The reaction of sulfone anions with trialkylboranes followed by thermal isomerization of the obtained boron compounds in the presence of excess borane-methyl sulfide complex and by alkaline hydroperoxide oxidation yields primary alcohols. 相似文献
338.
Youngchan Jang Dai Seung Choi Shin Han 《Journal of polymer science. Part A, Polymer chemistry》2004,42(5):1164-1173
The activation of a metal alkyl‐free Ni‐based catalyst with B(C6F5)3 was investigated in the polymerization of 1,3‐butadiene. A catalyst of bis(1,5‐cyclooctadiene)nickel (Ni(COD)2)/B(C6F5)3 was found to have high catalytic activity and 1,4‐cis stereoregularity. The catalyst was also found to provide polybutadiene having a molecular weight (Mw) of up to 117,000, even in the absence of AlR3 and MAO. Variations in the mol ratio of B(C6F5)3 to Ni affected catalytic activity, 1,4‐cis stereoregularity, and the Mw of polybutadiene, while the molecular weight distribution (MWD) of polybutadiene showed little correlation with the mol ratio of B(C6F5)3 to Ni. The use of other borane compounds such as B(C6H5)3, BEt3, and BF3 etherate in place of B(C6F5)3 clearly showed the two main functions of B(C6F5)3 in the present catalyst. The high Lewis acidity of B(C6F5)3 enabled it to activate catalytic complexes, thus inducing the polymerization. The steric bulkiness of B(C6F5)3 suppressed chain transfer reactions, contributing to the production of polybutadiene with a high Mw. Kinetic studies showed that the catalyst had an induction period, possibly due to the time needed for the formation of catalytic complexes starting from Ni(COD)2. A plot of ?ln (1?X), where X is the fractional conversion, as a function of time resulted in a linear relationship, showing that the present catalyst system followed first‐order kinetics with respect to monomer concentration. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1164–1173, 2004 相似文献
339.
340.
Amit Kumar Jacob S. A. Ishibashi Dr. Thomas N. Hooper Tanya C. Mikulas Prof. David A. Dixon Prof. Shih‐Yuan Liu Prof. Andrew S. Weller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(1):310-322
The coordination chemistry of the 1,2‐BN‐cyclohexanes 2,2‐R2‐1,2‐B,N‐C4H10 (R2=HH, MeH, Me2) with Ir and Rh metal fragments has been studied. This led to the solution (NMR spectroscopy) and solid‐state (X‐ray diffraction) characterization of [Ir(PCy3)2(H)2(η2η2‐H2BNR2C4H8)][BArF4] (NR2=NH2, NMeH) and [Rh(iPr2PCH2CH2CH2PiPr2)(η2η2‐H2BNR2C4H8)][BArF4] (NR2=NH2, NMeH, NMe2). For NR2=NH2 subsequent metal‐promoted, dehydrocoupling shows the eventual formation of the cyclic tricyclic borazine [BNC4H8]3, via amino‐borane and, tentatively characterized using DFT/GIAO chemical shift calculations, cycloborazane intermediates. For NR2=NMeH the final product is the cyclic amino‐borane HBNMeC4H8. The mechanism of dehydrogenation of 2,2‐H,Me‐1,2‐B,N‐C4H10 using the {Rh(iPr2PCH2CH2CH2PiPr2)}+ catalyst has been probed. Catalytic experiments indicate the rapid formation of a dimeric species, [Rh2(iPr2PCH2CH2CH2PiPr2)2H5][BArF4]. Using the initial rate method starting from this dimer, a first‐order relationship to [amine‐borane], but half‐order to [Rh] is established, which is suggested to be due to a rapid dimer–monomer equilibrium operating. 相似文献